| 1. |
- Li, Lizhen, 1977, et al.
(författare)
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Protective role of reactive astrocytes in brain ischemia.
- 2008
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Ingår i: Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism. - : SAGE Publications. - 0271-678X .- 1559-7016. ; 28:3, s. 468-81
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Tidskriftsartikel (refereegranskat)abstract
- Reactive astrocytes are thought to protect the penumbra during brain ischemia, but direct evidence has been lacking due to the absence of suitable experimental models. Previously, we generated mice deficient in two intermediate filament (IF) proteins, glial fibrillary acidic protein (GFAP) and vimentin, whose upregulation is the hallmark of reactive astrocytes. GFAP(-/-)Vim(-/-) mice exhibit attenuated posttraumatic reactive gliosis, improved integration of neural grafts, and posttraumatic regeneration. Seven days after middle cerebral artery (MCA) transection, infarct volume was 210 to 350% higher in GFAP(-/-)Vim(-/-) than in wild-type (WT) mice; GFAP(-/-), Vim(-/-) and WT mice had the same infarct volume. Endothelin B receptor (ET(B)R) immunoreactivity was strong on cultured astrocytes and reactive astrocytes around infarct in WT mice but undetectable in GFAP(-/-)Vim(-/-) astrocytes. In WT astrocytes, ET(B)R colocalized extensively with bundles of IFs. GFAP(-/-)Vim(-/-) astrocytes showed attenuated endothelin-3-induced blockage of gap junctions. Total and glutamate transporter-1 (GLT-1)-mediated glutamate transport was lower in GFAP(-/-)Vim(-/-) than in WT mice. DNA array analysis and quantitative real-time PCR showed downregulation of plasminogen activator inhibitor-1 (PAI-1), an inhibitor of tissue plasminogen activator. Thus, reactive astrocytes have a protective role in brain ischemia, and the absence of astrocyte IFs is linked to changes in glutamate transport, ET(B)R-mediated control of gap junctions, and PAI-1 expression.
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| 2. |
- Lundkvist, Andrea, 1975
(författare)
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The importance of astroglial cells in ischemia, regeneration and angiogenesis
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Astrocytes in the CNS communicate with both neurons and blood vessels. In many CNS pathologies, astrocytes respond by becoming reactive. Whether their performance at this stage is beneficial or detrimental for CNS function is unclear. The impact of reactive gliosis in brain ischemia and regeneration was studied using a mouse model where the astroglial reactivity is altered - these mice lack astroglial intermediate filaments (IFs), a part of the cytoskeleton. We found that reactive astrocytes provide protection in brain ischemia. However, they impose an obstacle for neuroregeneration. This mouse model was further utilized to study the function of astroglial IFs in the retina. For normal structure and function of the retina, IFs of astroglial cells are dispensable. However, upon exposure to extreme mechanical stress, they provide structural support to a specific part of the retina but, interestingly, in the ischemic retina, the absence of IFs diminishes the usual vascular lesions. Vision impairment in ischemia-induced retinopathies like diabetic retinopathy is caused by pathological angiogenesis - blood vessel formation. Astrocytes are highly involved in the pathogenesis, since they overexpress the angiogenic growth factor VEGF-A. The absence of astrocytic IFs does not affect the VEGF-A expression. During developmental angiogenesis, a mechanism by which astrocytes perform vascular guidance by means of VEGF-A was identified. The angiogenic sprout consists of two different endothelial cell populations: the tip-cell and stalk-cells. VEGF-A becomes deposited in a gradient like fashion at the front of the angiogenic sprout. This distribution is crucial for physiological vascular patterning, since it coordinates directed migration of tip-cells and proliferation by stalk cells. This concept was applied to a situation of pathological vascular patterning, i.e. the ischemic retina. We found that defective patterning is caused by disruption of VEGF-A gradients, where VEGF-A is liberated from the matrix by proteolytic enzymes, since inhibition of the activity of matrix-metalloproteases restores physiological vascular patterning.
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| 3. |
- Lundkvist, Andrea, 1975, et al.
(författare)
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Under stress, the absence of intermediate filaments from Müller cells in the retina has structural and functional consequences.
- 2004
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Ingår i: Journal of cell science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 117:Pt 16, s. 3481-8
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Tidskriftsartikel (refereegranskat)abstract
- In epithelial and muscle cells, intermediate filaments (IFs) are important for resistance to mechanical stress. The aim of this study was to elucidate whether IFs are also important for providing resistance to mechanical stress in the Müller cells of the retina and whether this has any pathophysiological consequences. We used mice deficient in IF proteins glial fibrillary acidic protein and/or vimentin (GFAP(-/-), Vim(-/-) and GFAP(-/-) Vim(-/-)), and stress on the retina was applied by excision of the eyes immediately post mortem (compared with in situ fixation) or by inducing a neovascular response to oxygen-induced retinopathy (OIR). The structure of unchallenged retinas was normal, but mechanical stress caused local separation of the inner limiting membrane (ILM) and adjacent tissue from the rest of the retina in GFAP(-/-) Vim(-/-) mice and, to a lesser extent, in Vim(-/-) mice. This detachment occurred within the endfeet of Müller cells, structures normally rich in IFs but IF-free in GFAP(-/-) Vim(-/-) mice. Hypoxia-induced neovascularization was comparable in all groups of mice with respect to the retinal surface area occupied by new vessels. However, the vessels traversed the ILM and penetrated the vitreous body less frequently than in wild-type retinas (31-55% in Vim(-/-), 66-79% in GFAP(-/-) Vim(-/-)). We conclude that IFs are important for maintaining the mechanical integrity of Müller-cell endfeet and the inner retinal layers under a mechanical challenge. Furthermore, the absence of IFs in Müller cells leads to an abnormal response of the vascular system to ischemia, specifically decreased ability of newly formed blood vessels to traverse the ILM.
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| 4. |
- Takemoto, Minoru, et al.
(författare)
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A new method for large scale isolation of kidney glomeruli from mice.
- 2002
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Ingår i: The American journal of pathology. - 0002-9440. ; 161:3, s. 799-805
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Tidskriftsartikel (refereegranskat)abstract
- Here we report a new isolation method for mouse glomeruli. The method is fast and simple and allows for the isolation of virtually all glomeruli present in the adult mouse kidney with minimal contamination of nonglomerular cells. Mice were perfused through the heart with magnetic 4.5- micro m diameter Dynabeads. Kidneys were minced into small pieces, digested by collagenase, filtered, and collected using a magnet. The number of glomeruli retrieved from one adult mouse was 20,131 +/- 4699 (mean +/- SD, n = 14) with a purity of 97.5 +/- 1.7%. The isolated glomeruli retained intact morphology, as confirmed by light and electron microscopy, as well as intact mRNA integrity, as confirmed by Northern blot analysis. The method was applicable also to newborn mice, which allows for the isolation of immature developmental stage glomeruli. This method makes feasible transcript profiling and proteomic analysis of the developing, healthy and diseased mouse glomerulus.
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